javascript - 类发现未定义的 img src

Question

因此，我尝试从中定义变量并将其放入初学者警报中的 img src 的 html 代码如下所示:

<img class="ProductItem-gallery-slides-item-image" data-load="false" data-src="https://static1.squarespace.com/static/58068e2f5016e12d2c5502ff/5807a2df8419c2ae30bc4d69/5a3dd5740852297f08f5a12c/1529335692585/White-Goldie-V-neck-Tee.jpg" data-image="https://static1.squarespace.com/static/58068e2f5016e12d2c5502ff/5807a2df8419c2ae30bc4d69/5a3dd5740852297f08f5a12c/1529335692585/White-Goldie-V-neck-Tee.jpg" data-image-dimensions="750x1124" data-image-focal-point="0.5,0.5" data-position-mode="standard" data-parent-ratio="0.7" alt="White" src="https://static1.squarespace.com/static/58068e2f5016e12d2c5502ff/5807a2df8419c2ae30bc4d69/5a3dd5740852297f08f5a12c/1529335692585/White-Goldie-V-neck-Tee.jpg?format=500w" style="font-size: 0px; left: -0.312278px; top: 0px; width: 327.625px; height: 491px; position: relative;" id="yui_3_17_2_1_1530976058504_955" data-image-resolution="500w">

我正在尝试使用以下内容获取 img src

 var picture = document.getElementsByClassName("ProductItem-gallery-slides-item-image loaded").src;
 alert(picture);

返回

Undefined 

我会提到img src位于多个div的深处，其ID是随机的。

Answer 1

获取 document.getElementsByClassName() 返回一个数组，请尝试以下操作:

document.getElementsByClassName("ProductItem-gallery-slides-item-image loaded")[0].src;

工作示例:

var picture = document.getElementsByClassName("ProductItem-gallery-slides-item-image loaded")[0].src;
 alert(picture);

<img class="ProductItem-gallery-slides-item-image loaded" data-load="false" data-src="https://static1.squarespace.com/static/58068e2f5016e12d2c5502ff/5807a2df8419c2ae30bc4d69/5a3dd5740852297f08f5a12c/1529335692585/White-Goldie-V-neck-Tee.jpg" data-image="https://static1.squarespace.com/static/58068e2f5016e12d2c5502ff/5807a2df8419c2ae30bc4d69/5a3dd5740852297f08f5a12c/1529335692585/White-Goldie-V-neck-Tee.jpg" data-image-dimensions="750x1124" data-image-focal-point="0.5,0.5" data-position-mode="standard" data-parent-ratio="0.7" alt="White" src="https://static1.squarespace.com/static/58068e2f5016e12d2c5502ff/5807a2df8419c2ae30bc4d69/5a3dd5740852297f08f5a12c/1529335692585/White-Goldie-V-neck-Tee.jpg?format=500w" style="font-size: 0px; left: -0.312278px; top: 0px; width: 327.625px; height: 491px; position: relative;" id="yui_3_17_2_1_1530976058504_955" data-image-resolution="500w">